This is definitely off topic as it applied to roller brakes, but Rudge-Whitworth used to link the brakes using a tiny version of the excellent linked braking on their motorcycles. The rear brake operated via a spring so that there was a limit to the amount of braking on the rear wheel. It sounds Heath Robinson (Rube Goldberg for US readers) but on the motorcycle it was very effective. Lightweight content? Not much but it was used on the nineteen twenties dropped bar bikes using a short pull up front brake and dwarf levers. Stuart Tallack in West Sussex.